PORTFOLIO

Electromagnetic flow meters in sand dredging

Electromagnetic flow meters in sand dredging

While many electromagnetic flow meter applications involve water, solutions and relatively light suspensions, there are others in which the material being pumped through pipes is very heavy indeed. And flow materials don’t come much heavier – or more abrasive – than sand.

I was very interested to read a case study from America concerning the Carolina Sand company and its dredging process, which was improved with the help of pumping specialist Hagler Systems of North Augusta.

The installation of accurate, stable flow meters was a key factor in doubling the company’s average production rate to an impressive 300 tons an hour. Their role in this application is not only to monitor flow rate but to control it, by sending signals to the pump controller which result in the pump being speeded up or slowed down to maintain the optimum flow.

For this system to work, the flow meter reading has to be reliable. A false reading would result in the wrong pumping speed. If the sand flows too slowly, productivity falls. It if flows too quickly, the pipeline can become choked and may take several days to clear – which is a very serious stoppage.

In selecting the flow meters, one immediate decision was to go for DC rather than AC, as AC magmeters are more prone to drifting and giving false results when confronted with a mix of sand and rock. Proven ability to deliver stable readings, to within a tenth of a gallon per minute, was essential.

The ability to withstand abrasion was another obvious consideration. The meters were customised to match the interior dimensions of the pipeline precisely, so that the meter itself would have no influence on the sand’s flow and wear of the meter would be minimised.

With the right choice of meters, the operation is now running very smoothly, without downtime, and the cost savings in fuel, electrical supply and manpower alone have covered their installation.